1. Field of the Invention
This invention relates to a curable epoxy resin composition which can be used for treating the surface of an object to impart repellency to water or ink thereto, in particular, an epoxy resin composition which can form a patterned film by ultraviolet light irradiation and can form a cured film part of which can be selectively removed by using excimer laser etc. The present invention also relates a method for treating the surface of a base material using the above composition, an ink-jet recording head subjected to ink repellent treatment using the above composition and an ink-jet apparatus using the above recording head.
2. Related Background Art
In various fields, it is well known to provide a water repellent coating to a member requiring water resistance or ink repellency to impart such properties thereto, and resin materials and coatings for such applications have been developed.
For example, films made of a fluorine-base coating having a perfluoro group or fluoroolefin are extremely stable thermally and chemically, have excellent resistance to weather, water, chemicals and solvents, and in addition, have excellent release properties, abrasion resistance and water repellency. Thus they are widely used in various applications.
On the other hand, in the ink-jet recording head, which ejects minute ink droplets from an ink ejection orifice to attach them on paper etc. for recording or image formation, upgrading has been carried out to achieve higher recording properties with much smaller liquid droplets, higher driving frequency and more nozzles so on. Therefore, treatment to keep the conditions of an orifice plate on which nozzles are facing, is getting important more and more.
However, it is difficult to carry out precise surface treatment selectively or in a pattern to repel ink from the orifice plate with conventional materials. The reason is as follows: to achieve the above purpose, the main component of the treating agent must be a compound having photosensitive functional group so that the treating agent can have photoresist properties, and it is difficult to design a compound to have both photosensitive functional groups and water and ink repellency.
Even if the orifice plate could be treated with a conventional fluorine base material, it is still necessary to design a film structure to keep the surface properties for a long time. Accordingly, a material that has the above-described performance and patternable properties will be extremely valuable in surface treatment of ink-jet recording heads.
In the ink-jet recording system where recording is performed by ejecting ink as ink droplets, a preferable ink ejection orifice (opening) of a nozzle is designed so that:                (1) after ink ejection, the remaining ink in the ink column can be swiftly stored in the nozzle;        (2) ink droplets attached to the surface of the orifice plate can be wiped off easily by cleaning operation;        (3) the surface of the orifice plate can be resistant to abrasion due to cleaning operation to wipe the ink attached to the surface or due to paper conveyance;        (4) the meniscus can be always formed at the nozzle orifice (refer to FIG. 1, reference numeral 23) in the repeated droplet formation and ink re-fill;        (5) ink can be ejected in a direction normal to the meniscus;        (6) the nozzle has an interfacial tension or contact angle that allows meniscus formation even with an ink having a low surface tension or under a slightly negative pressure state.        
The reason why such performance is required for the ink ejection orifice is that the printing performance is directly related to the attachment of ink to the vicinity of the orifice because if a recording liquid such as ink is attached in the vicinity of the liquid ejection orifice, the flying direction of the ejected liquid droplet deviates from the desired direction impairing high precision printing. One of the means for preventing liquid attachment to the area surrounding the liquid ejection orifice that causes the above-described deviation in the direction of ejection is to treat the orifice plate with a water repellant. For example, it is known a method in which ink repellent treatment is performed using a polymer having fluoroacetyl group and silazane group (Japanese Patent Application Laid-Open No. 2-39944).
On the other hand, with increasing demands for higher-quality image recording by a printer using a liquid-jet recording system, more improved properties are required for the recording liquid. Accordingly, pH of the recording liquid is often adjusted to 7 to 11 in order to improve the solubility or dispersion stability of the components. Thus, it is desired to employ structural materials having resistance to alkali and hydrolysis for printer members.